Electric power is generally transmitted from generation plants to end users (residential, commercial, and industrial (C&I), etc.) via a transmission and distribution grid consisting of a network of power stations, transmission circuits, and substations interconnected by powerlines. Once at the end users, electricity can be used as energy to power any number of devices. Controlling peak energy demand/consumption is beneficial to both utilities and to consumers. For instance, electrical utility companies design their systems, including generation, transmission, and distribution, to maintain grid stabilization and also to account for peak energy demand, which specifically often results in under-utilized systems for a vast majority of time.
A Demand Response (DR) system is a smart grid application mechanism generally designed to reduce power consumption, e.g., during peak hours. A utility or a service provider may issue a DR request to its customers asking them to turn off non-critical devices when power demand may exceed supply or when utilities may need to purchase power at a higher cost than the rate they are allowed to charge. Since utilities continuously balance energy demand with supply, DR can be viewed as complementary to energy generation and transmission capacity, as it provides utilities with a manner to control energy demand and bring it in line with the available power.
Generally, the end-device reaction to a DR request has been for each end-device to shut down (or reduce power), and then restart at a later, e.g., randomized, time. The response of end-devices in this manner, however, has limited intelligence, and may not be suitable for specific situations where greater control may be particularly beneficial and/or necessary.
Additionally, the transfer of alternating-current (AC) electric power to the end users most frequently takes the form of polyphase electric power, where, e.g., three voltage waveforms are produced that are generally equal in magnitude and 120° out of phase to each other. If the load on a three-phase system is balanced equally (enough) among the phases, little or no current flows through a neutral point, which is an important design aspect of the electric grid, allowing for efficient use of transformer capacity, reduced materials (e.g., size of a neutral conductor to handle imbalance), etc. However, there are many factors that may create imbalance and/or instability between the phases, such as unequal loads, excess load usage, faults, downed power-lines, etc.